Silica dust controls for hydraulic fracturing operations

ABSTRACT

A system for controlling dust during hydraulic fracturing operations includes a manifold having a plurality of ports for capturing dust when negative air pressure is applied to the manifold. A support frame positions the manifold above a piece of hydraulic fracturing equipment receiving sand from a sand source.

CROSS-REFERENCE TO RELATED APPLICATION

The present application is a continuation of U.S. patent applicationSer. No. 15/164,577, filed May 25, 2016, which is a continuation-in-partof U.S. patent Ser. No. 14/862,354, filed Sep. 23, 2015, which is acontinuation of application Ser. No. 14/527,868, filed Oct. 30, 2014,which is a divisional of U.S. patent application Ser. No. 14/178,782,filed Feb. 12, 2014, which is a continuation of U.S. patent applicationSer. No. 13/769,456, filed Feb. 18, 2013, all of which are incorporatedherein by reference for all purposes.

FIELD OF INVENTION

The present invention relates in general to hydraulic fracturing, and inparticular to systems and methods for controlling silica dust during thehandling of frac sand.

BACKGROUND OF INVENTION

Hydraulic fracturing (“fracing”) is a well known technique for releasingoil and natural gas from underground reservoirs within rock formationshaving a limited permeability. For example, fracing is often used torelease oil and natural gas, such as natural gas or oil, from shaleformations.

Fracing is a well completion technique performed after the drilling ofthe wellbore, which in the case of releasing natural gas from shale, iscommonly a horizontal wellbore, although occasionally the wellbore isvertical. Fracing fluid, which is primarily water and chemicals thatform a viscous gel, is pumped into the well to create fractures withinthe surrounding rock. The viscous gel carries a “proppant” into thefractures, such that when the pumping stops, the fractures remainsubstantially open and allow the oil and natural gas to escape into thewellbore.

One typical proppant is “frac sand.” Frac sand is normally high puritysilica sand with grains having a size and shape capable of resisting thecrushing forces applied during the closing of the fractures when thehydraulic force provided by the pumping is removed. However, given thatfrac sand contains a high proportion of silica, the loading,transportation, and unloading of frac sand presents significant safetychallenges.

The United States Occupational Safety and Health Administration (“OSHA”)lists silica as a carcinogen. In particular, the exposure and inhalationof silica dust has been linked to silicosis, which is an irreversiblelung disorder characterized by inflammation and scarring of the upperlobes of the lungs. The best, and perhaps only way, to reduce oreliminate the threat of silicosis is to carefully control workerexposure to silica dust.

OSHA lists a number of different ways to limit worker exposure to silicadust, including limiting worker time at a worksite, limiting the numberof workers at a worksite, watering roads and other worksite areas,enclosing points where silica dust is released, and requiring workers towear respirators. These techniques do not, at least on their own,provide a complete solution to the problem of controlling silica dust.Furthermore, these existing techniques, while commendable, arenonetheless burdensome, time-consuming, inefficient, and impractical.

SUMMARY OF INVENTION

One representative embodiment of the principles of the present inventionis a system for controlling dust during hydraulic fracturing operations,which includes a manifold having a plurality of ports for capturing dustwhen negative air pressure is applied to the manifold. A supportstructure positions the manifold above a piece of hydraulic fracturingequipment receiving sand from a frac sand source.

Another representative embodiment is a system for controlling dustduring hydraulic fracturing operations, which includes a supportstructure and a manifold positioned by the support structure above apiece of frac sand handling equipment receiving frac sand from a fracsand source. An enclosure supported by the support structure encloses atleast a portion of the piece of frac sand handling equipment. At leastone conduit in fluid communication with the manifold has an inlet forcapturing dust contained within the enclosure when negative air pressureis applied to the manifold.

A further exemplary embodiment of the present principles is a frac sandhandling system including frac sand handling equipment, and a supportstructure. An enclosure is supported by the support structure andencloses at least a portion of the frac sand handling equipmentincluding a point at which frac sand is received by the frac sandhandling equipment. A manifold is positioned by the support structureabove the frac sand handling equipment. The manifold includes aplurality of ports for capturing dust when negative air pressure isapplied to the manifold, with at least one of the ports adapted tocapture dust generated around the point at which frac sand is receivedby the frac sand handling equipment.

The present inventive principles advantageously provide for efficientand flexible systems and methods for collecting the silica dustgenerated during the offload of frac sand from a frac sand source, suchas a sand transport and storage trailer, a vertical sand mover, or oneor more containers positioned directly above the lateral conveyor. Amongother things, by positioning the manifold above the lateral handlingequipment (e.g., blender bin and/or tub, t-belt, or dragon tail) theoverall profile of the enclosure and manifold system becomes morecompact. As a result, the amount of dust control system equipment on ornear the ground can be reduced, which reduces tripping hazards, reducesclutter, and increases accessibility to both the dust control system andthe associated frac sand handling equipment.

The manifold, support structure, and enclosure can be configured tocontrol dust generated in and around various pieces of frac sandhandling equipment such as lateral conveyors (t-belts), angled liftingconveyors (dragon tails), and blenders, as well as differentcombinations of those pieces of equipment.

The support structure allows the manifold to either be suspended fromthe support structure using a cable or strap or supported at a point onthe support structure itself. The support structure may be free-standingsuch that other equipment within the frac sand handling and dust controlsystem can be moved or reconfigured without the need to move orreconfigure the manifold, support structure, and/or enclosure.

The support structure also allows the manifold to be positioned insideor outside of the enclosure that contains dust generated duringoperation of the frac sand handling equipment. In embodiments in whichthe manifold is positioned inside the enclosure, air flow into themanifold can be achieved through a simple aperture through the manifoldwall, through a fitting adapted to connect with a flexible conduit, withor without the flexible conduit attached, or through an extended fittingor rigid conduit.

The application of these principles improves the efficiency andflexibility of the frac sand offloading process by allowing increasedworker time at the worksite and/or for more workers to be present at theworksite at one time, reducing the need for watering of worksite areasand the enclosure of points where silica dust is released, reducing theneed for respirator wear, and decreasing the amount of silica dustintake by the engines of nearby vehicles and equipment.

BRIEF DESCRIPTION OF DRAWINGS

For a more complete understanding of the present invention, and theadvantages thereof, reference is now made to the following descriptionstaken in conjunction with the accompanying drawings, in which:

FIG. 1 is a perspective diagram of a representative frac sandtransportation and unloading system including a frac sand silica dustcontrol system according to a preferred embodiment of the principles ofthe present invention;

FIG. 2 is a plan view diagram of the frac sand transportation andunloading system of FIG. 1, which emphasizes the airflow paths throughthe frac sand silica dust control system;

FIG. 3 is a plan view diagram of the frac sand transportation andunloading system of FIG. 1, which generally indicates the locations ofparticular structures of the frac sand silica dust control subsystemshown in more detail in FIGS. 4-6;

FIG. 4A is a diagram showing in further detail the pneumatic connectionsbetween the inlets of the silica dust control unit and the manifolds ofFIG. 1;

FIG. 4B is a diagram showing in further detail the direct airflow pathbetween the silica dust control unit and the silica dust control conduitsubsystem servicing one selected trailer of FIG. 1;

FIG. 4C is a diagram showing in further detail the pneumatic connectionbetween a selected manifold and the silica dust control conduitsubsystem serving another selected trailer of FIG. 1;

FIG. 4D is a diagram showing in further detail the pneumatic connectionsbetween a selected manifold and the silica dust capture hose controllingsilica dust generated during the operation of a corresponding trailerdischarge conveyor shown in FIG. 1;

FIG. 4E is a diagram showing in further detail the pneumatic connectionsbetween a selected manifold and the silica dust capture hosescontrolling silica dust generated by the system discharge conveyor ofFIG. 1;

FIG. 5A is a diagram showing in further detail a selected silica dustcapture hose controlling silica dust generated by the discharge of fracsand from the tank of representative trailer to the base of thecorresponding trailer discharge conveyor shown in FIG. 1;

FIG. 5B is a diagram showing in further detail a selected silica dustcapture hose controlling silica dust generated by the discharge of fracsand from the outlet of a corresponding representative trailer conveyorto the lateral transfer conveyor section of FIG. 1;

FIG. 5C is a diagram showing the hoses controlling silica dust generatedduring the movement of sand by the upwardly angled conveyor section ofFIG. 1 to a point above the bin of the blender of FIG. 1, along with thesilica dust capture hose controlling silica dust generated during thedischarge of sand into the blender bin from the conveyor section spout;

FIG. 6A is a diagram showing in further detail the pneumatic connectionsof the silica dust control conduit subsystem of a representative one ofthe trailers of FIG. 1;

FIG. 6B is a diagram showing in further detail one of the T-fittingsinterconnecting the air conduits of the silica dust control conduitsubsystem shown in FIG. 6A;

FIG. 6C is a diagram showing one of the end fittings terminating the airconduits of the silica dust control conduit subsystem shown in FIG. 6A;

FIG. 6D is a diagram showing the four-way fitting interconnecting theair conduits of the silica dust control subsystem of one particulartrailer with the silica dust control unit, as shown in FIG. 4B;

FIG. 7A is a diagram showing an alternative embodiment of the principlesof the present invention in which a cover is provided over portions ofthe representative frac sand transportation and unloading system of FIG.1 for containing silica dust generated during movement of sand throughthe system;

FIG. 7B is a conceptual diagram providing a first detailed view of arepresentative embodiment of the cover shown in FIG. 7A;

FIG. 7C is a conceptual diagram providing a second detailed view of therepresentative embodiment of the cover shown in FIG. 7A;

FIG. 8A is a perspective view diagram of a representative raisedmanifold system according to the principles of the present invention,which is suitable for use in a frac sand silica dust control system,such as that shown in FIG. 1;

FIG. 8B is an end elevational view diagram of the raised manifold systemof FIG. 8A;

FIG. 8C is a diagram providing a more detailed side elevational view ofa portion of the raised manifold system of FIG. 8A along with arepresentative number of attached dust collection conduits;

FIG. 8D is a perspective view diagram of the raised manifold system ofFIG. 8A shown connected to an associated air movement system anddisposed within an enclosure suitable for containing dust generatedalong the lateral conveyor and/or lifting conveyor of FIG. 1;

FIG. 8E is a side elevational view diagram showing a representative useof the raised manifold and enclosure system of FIGS. 8A-8D in the systemof FIG. 1, wherein the lateral conveyor is enclosed and flexibleconduits attached to the raised manifold collect dust generated atpoints along the lateral conveyor and from within the sandtransportation and storage containers;

FIG. 8F is a perspective view diagram of an alternative raised manifoldand enclosure system according to the principles of the presentinvention, which is suitable for use in a frac sand silica dust controlsystem such as that shown in FIG. 1;

FIG. 8G is a side elevational view diagram showing a representative useof the raised manifold and enclosure system of FIG. 8F in the system ofFIG. 1, wherein the lateral conveyor is enclosed and flexible conduitscollect dust generated along the lateral conveyor and from within thetransportation and storage containers;

FIG. 8H is a perspective view diagram of another alternative raisedmanifold and enclosure system according to the principles of the presentinvention, which is suitable for use in a frac sand silica dust controlsystem such as that shown in FIG. 1;

FIG. 8I is a top plan view diagram of an alternative sand transportationand unloading system including a frac sand silica dust control systemusing the raised manifold and enclosure system of FIGS. 8A-8D;

FIG. 9A is a side elevational view diagram of another alternative raisedmanifold and enclosure system according to the inventive principles andsuitable for containing dust generated in and around a blender bin,blender tub, or both, in a dust control system such as that shown inFIG. 1;

FIG. 9B is an end elevational view diagram of the raised manifold andenclosure system shown in FIG. 9A, as connected to an air system such asthat shown in FIG. 1;

FIG. 9C is a perspective view diagram of the raised manifold andenclosure system of FIGS. 9A-9B, shown connected to an air system suchas that shown in FIG. 1;

FIG. 9D is a perspective view diagram of a further alternative raisedmanifold and enclosure system according to the inventive principles, asconnected to an air system such as that shown in FIG. 1; and

FIG. 9E is a perspective view diagram of an additional alternativeraised manifold and enclosure system according to the inventiveprinciples, as connected to an air system such as that shown in FIG. 1;

FIG. 9F is a top plan view diagram of an alternative sand transportationand unloading system including a frac sand silica dust control systemusing the raised manifold and enclosure system of FIGS. 9A-9C.

DETAILED DESCRIPTION OF THE INVENTION

The principles of the present invention and their advantages are bestunderstood by referring to the illustrated embodiment depicted in FIGS.1-9 of the drawings, in which like numbers designate like parts.

FIG. 1 is a diagram of an exemplary frac sand transportation, storage,and unloading system 100 including a frac sand silica dust controlsystem according to a preferred embodiment of the principles of thepresent invention. System 100 is also shown in the plan views of FIGS. 2and 3, with FIG. 2 emphasizing the air flow paths of the silica dustcontrol system and FIG. 3 generally showing the locations of particularfeatures of the silica dust control system shown in further detail inFIGS. 4-6.

Generally, system 100 is assembled at a hydraulic fracturing worksiteand is used to offload frac sand transported to the worksite from a fracsand supplier via trailers and offloaded into a blender. The blendermixes the sand with the water and chemicals to form the fracing fluid.Given the significantly large amounts of frac sand that are typicallyrequired during typical hydraulic fracturing operations, a substantialamount of potentially hazardous silica dust is commonly generated duringconventional trailer offloading operations. The principles of thepresent invention advantageously provide for the control of frac sandproduced silica dust, which consequently improves personnel safety,helps reduce the need for respirators and other burdensome safetyequipment, and allows personnel to work longer and more efficiently atthe worksite.

In the illustrated embodiment of system 100 shown in FIGS. 1, 2, and 3,four (4) conventional sand storage trailers 101 a-101 d are shown at afracing worksite. While four (4) trailers 101 are shown as an example,the actual number of sand storage trailers 101 utilized in anyparticular embodiment or configuration of system 100 may vary based onthe needs and restrictions at the worksite. The size and configurationof system 100 in any given worksite application will depend on suchfactors as the amount of sand that must be offloaded, the speed at whichsand must be offloaded, and the size and capabilities of the offloadingconveyor system. In the illustrated embodiment of system 100, eachtrailer 101 includes a retractable trailer discharge conveyor (transferbelt) 102 a-102 d, which receives sand from the compartments of thetrailer internal tank via a lateral transfer belt running underneath thetrailer tank (not shown). Trailers 101 are, for example, Sand King3000/4000 frac sand trailers from Convey-All Industries, Inc., althoughthere are a number of other commercially available sand storage trailersknown in the art. It should also be recognized that the principles ofthe present invention are also applicable to embodiments of system 100in which sand is stored and discharged from other types of fixed andtransportable storage systems, such as tanks, silos, compartmentedvehicles, and so on.

Each trailer discharge conveyor 102 a-102 d discharges sand to aconventional transportable conveyor system, for example, Unibeltconveyor system from Convey-All Industries, Inc., which includes acontinuous transfer belt running through a lateral conveyor section 103and a upwardly angled discharge conveyor section 105. During typicaloffloading operations, one or more randomly selected trailers 101discharge sand to the lateral conveyor section 103 at a given time.

Sand being discharged by each trailer discharge conveyor 102 a-102 dfalls through slots 104 and onto lateral conveyor section 103. Lateralconveyor section 103 then carries the sand to upwardly angled dischargeconveyor section 105, which discharges the sand to a bin of a blendertruck 119 (FIGS. 3 and 5C), which mixes the sand with water andchemicals in quantities needed for the formulation of the particularfracing fluid being used.

The amount of sand being transferred at any one time in system 100 canbe substantial. For example, a Convey-All Unibelt conveyor can nominallytransfer and discharge 22,000 pounds per minute of sand from trailers101 a-101 d. The generation of a corresponding substantial amount offine silica dust is a natural consequence of this transfer and dischargeprocess.

According to the principles of the present invention, silica dustgenerated during the offloading of trailers 101 a-101 d is collected bysuction at selected points around system 100 most susceptible to thegeneration and discharge of silica dust. In the preferred embodiment,silica dust is collected: (1) within the compartments of the tanks oftrailers 101 a-101 d; (2) at the base of each trailer discharge conveyor102 a-102 d, near the point at which sand is received from the trailerlateral conveyor and the trailer tanks; (3) at the point sand isdischarged from trailer discharge conveyors 102 a-102 d through slots104 and onto lateral conveyor section 103; (4) at multiple points alongupwardly-angled discharge conveyor section 105; and (5) near the pointsand is discharged from the spout of discharge conveyor 105 in to thebin of blender 119. It should be noted that in alternative embodiments,silica dust may be collected at additional points, or even fewer points,within system 100, as required.

The silica dust control function of system 100 is driven by a silicadust control unit 106, which draws silica dust-bearing air collected atpoints across the system though a pair of large manifolds 107 and 108.In the illustrated embodiment of system 100, silica dust control unit106 also draws silica dust-bearing air directly from trailer 101 dthrough flexible hosing 109, although this is not a strict requirementof the principles of the present invention. Silica dust control unit106, which may include a baghouse and/or cyclone, separates the silicadust from the air and discharges substantially silica dust-free air intothe surrounding environment. One exemplary silica dust control unit,suitable for use as silica dust control unit 106 of system 100, is anETI Cyclone 20 DC system, available from Entech Industries, whichincludes multiple twenty-inch (20″) inlets and produces a nominalairflow of 20000 cubic feet per minute (cfm).

Silica dust control unit 106 establishes airflow in the direction shownby arrows in FIG. 2. In the preferred embodiment, two intake ports ofsilica dust control unit 106 are pneumatically connected with manifolds107 and 108, which run along corresponding sides of lateral conveyorsection 103, and one intake port of silica dust control unit 106 isdirectly pneumatically connected to trailer 101 d through flexiblehosing 109.

Silica dust generated in each of the compartments of trailers 101 a-101d is collected through a corresponding set of fittings 110 a-110 f andhoses 111 a-111 e. In the illustrated embodiment of system 100, thecompartments of trailers 101 a-101 c are pneumatically coupled tomanifold 107 through flexible hosing 113 a-113 c. For trailer 101 d, onefitting 110 is replaced with a four-way fitting 112, which directlypneumatically couples the compartments of trailer 101 d with silica dustcontrol unit 106.

Flexible hoses 114 a-114 c, which tap manifold 107, and the flexiblehose 114 d, which taps manifold 108, collect silica dust at the bases ofeach trailer discharge conveyor 102 a-102 d. Flexible hoses 115 a-115 d,which tap manifold 108, collect silica dust at the discharge points oftrailer discharge conveyor 102 a-102 d into slots 104 a-104 c of lateralconveyor section 103. Flexible hoses 116 a-116 d, which tap manifold108, collect silica dust moving up upwardly angled discharge conveyorsection 105. It should be noted that the pneumatic paths between silicadust collection hoses 113, 114, 115, and 116 and silica dust controlunit 106 may vary between embodiments of system 100. In the preferredembodiment of system 100 shown in FIG. 1, the tapping point, as well asthe manifold 107 or 108 being tapped, minimizes the lengths of manifolds107 and 108 and silica dust collection hoses 113, 114, 115, and 116.Generally, so long as sufficient suction is available at a given silicadust collection point, the manifold 107 or 108 tapped, the point on themanifold 107 or 108 tapped the corresponding flexible hose, or both, maybe varied.

A flexible hose 117, which taps manifold 107, captures silica dustgenerated by the discharge of sand from upwardly angled dischargeconveyor 105 into the bin of blender 119. (While flexible hose 117 tapsmanifold 107, in alternative embodiments flexible hose 117 may tapmanifold 108).

Manifolds 107 and 108 include a number of straight sections 120 and bentor curved sections 121 and are preferably constructed as tubes or pipesof rigid metal, such as aluminum. Rigid metal embodiments providedurability, particularly when manifolds 107 and 108 sit on or close tothe ground and/or are exposed to contact by personnel or to otherstructures within system 100. However, in alternative embodiments,manifolds 107 and 108 may be constructed, either in whole or in part,from sections of semi-rigid conduit or flexible (corrugated) hose. Forexample, semi-rigid conduit or flexible hose may be used in sections 121of manifolds 107 and 108 that must be bent to provide a path around,over, or under, other structures in system 100.

Preferably, manifolds 107 and 108 are each constructed in multiplestraight sections 120 and multiple bent or curved sections 121, whichare clamped together using conventional clamps. This preferredconstruction allows manifolds 107 and 108 to be efficiently assembledand disassembled at the worksite, allows the most direct paths to betaken to silica dust control unit 106, and allows the overall system ofconduits to be adapted to different configurations of system 100 (e.g.,different types and number of trailers 101, different transportableconveyor systems, different surface conditions).

Additionally, the diameters of the various sections of manifolds 107 and108 may increase or decrease, depending on the airflow provided by thegiven silica dust control unit 106. The diameters of manifolds 107 and108 are determined by a number of factors, including the intakediameters of silica dust control unit 106, the airflow produced bysilica dust control unit 106, and the amount of suction needed at thesilica dust collection points. Similarly, the diameters of silica dustcollection hoses 113, 114, 115, and 116 will depend on factors such asthe airflow available from silica dust control unit 106, the diametersof manifolds 107 and 108, and the amount of suction required at a givenhose inlet. In one typical embodiment of system 100, manifolds 107 and108 have a nominal diameter of twenty inches (20″) and silica dustcollection hoses 113, 114, 115, and 116 are nominally within the rangeof six to sixteen inches (6″-16″) in diameter. In other words, theprincipals of the present invention advantageously allow for variationsin the components and configuration of system 100.

It should be recognized that the transportable conveyor system,including lateral conveyor section 103 and discharge conveyor section105, is not always required. In this case, one or more trailer dischargeconveyors 102 discharge sand directly from the corresponding trailers101 into the bin of blender 119. In embodiments of system 100 that donot utilize the transportable conveyor system, only a correspondingnumber of flexible hoses 114 and 115 are required for collecting silicadust at the base and outlet of each trailer discharge conveyor 102discharging to blender 119. (Along with the desired connections forremoving dust within the trailers 101 themselves.) Advantageously, onlysingle manifold 107 or 108 may be required in these embodiments.

FIG. 4A is a more detailed diagram showing the pneumatic connectionsbetween manifolds 107 and 108 and silica dust control unit 106. FIG. 4Bshows the direct pneumatic connection between trailer 101 d and silicadust control unit 106 through flexible hose 109 in further detail.

FIGS. 4C-4E illustrate representative tapping points between the heavierrigid sections 120 of manifolds 107 and 108 and selected flexible hosesutilized in system 100. In particular, FIG. 4C shows a representativepneumatic connection between manifold 107 and hose 113 c collectingsilica dust from the tank compartments of trailer 101 c. FIG. 4D showsrepresentative pneumatic connections between manifold 108 and hose 114d, which collects silica dust generated at the base of trailer dischargeconveyor 102 d, and hoses 115 c and 115 d, which collect silica dustgenerated at corresponding outlets of trailer discharge conveyors 102 cand 102 d. FIG. 4E shows representative pneumatic connections betweenmanifold 108 and hoses 116 a-116 d collecting silica dust generated bydischarge conveyor section 105.

As well known in the art, numerous techniques are commonly utilized forconnecting flexible hose with a rigid conduit or pipe, many of which aresuitable for use in system 100. In the illustrated embodiment shown inFIGS. 4C-4D, an aperture is tapped through the wall of the givenmanifold 107 or 108 and the lower periphery of a fitting (e.g., aluminumor steel pipe) 401 is attached, for example, by welding or brazing. Thelower section of a coupling 402 is attached to the upper periphery offitting 401, for example by welding or brazing. The tubular uppersection 403 of coupling 402 is received with the periphery of thecorresponding hose, which is then clamped in place by one or moreconventional clamps 404. When necessary, an extension or elbow (notshown) may be provided between upper section 403 of coupling 402 and thecorresponding hose. Similarly, a reduction coupling (see FIG. 5A,designator 501) may be provided between upper section 403 and coupling402, as required to transition to the selected hose diameter.

In the preferred embodiment shown in FIGS. 4C-4E, each coupling 402includes a slide gate, which provides for air flow control between thegiven silica dust capture hose 113, 114, 115, and 116 and thecorresponding manifold 107 or 108. In addition to allowing control ofthe amount of suction produced at the capture hose inlet, these slidegates also allow any unused taps to manifolds 107 and 108 to becompletely shut off, particularly when a hose is not connected tocoupling 402.

FIG. 5A depicts in further detail representative silica dust collectionhose 114 b collecting silica dust generated at the base of trailerdischarge conveyor 102 b. Hose 114 b pneumatically couples with manifold107 through a reduction coupling 501. The inlet end of hose 114 b, whichincludes an optional nozzle or shroud 502, is disposed proximate thepoint where the lateral conveyor of trailer 101 b discharges sand to thebase of trailer discharge conveyor 102 b. Silica dust generated duringsand transfer is captured by the suction created by silica dust controlunit 106 at the discharge end of hose 114 b and carried through manifold107 to silica dust control unit 106 to be filtered from the air. Silicadust collection hoses 114 a, 114 b, 114 c, and 114 d, which respectivelycollect silica dust generated at the bases of trailer dischargeconveyors 102 a, 102 b, 102 c and 102 d, are similar in configurationand operation.

FIG. 5B depicts in further detail representative silica dust collectionhose 115 b collecting silica dust generated during the discharge of sandfrom trailer discharge conveyor 102 b into lateral conveyor section 103.In the illustrated embodiment, trailer discharge conveyor 102 bdischarges through a section of flexible hose (conduit) 503 into thecorresponding slot 104 of lateral conveyor section 103. The inlet 504 ofsilica dust collection hose 115 b is disposed proximate the outlet offlexible hose 503. The suction produced by silica dust control unit 106gathers silica dust generated during the transfer of sand, which inturns moves to silica dust control unit 106 for filtering throughmanifold 108. The configuration and operation of silica dust collectionhoses 115 a, 115 b, 115 c, and 115 d, which respectively collect silicadust from the discharge points of trailer conveyors 102 a, 102 b, 102 c,and 102 d into lateral conveyor section 103 are similar.

Silica dust collection hoses 116 a-116 d, and the suction generated bysilica dust control unit 106, collect silica dust generated by thelifting and discharge of sand by discharge conveyor section 105. Asshown in FIG. 5C, silica dust collection hoses 116 a-116 d extend fromapertures through the body of discharge conveyor section 105 at selectedspaced-apart points. During operation, silica dust generated as sandmoves upwards towards the outlet spout is removed through silica dustcollection hoses 116 a-116 d and manifold 108 for filtering by silicadust control unit 106.

FIG. 5C also one possible configuration for flexible 117 with respect tothe spout of upwardly angled conveyor 105. Generally, the intake end offlexible hose 117 is located near the discharge point of the spout ofconveyor 105 and creates an updraft, which captures silica dustgenerated as sand falls into the bin of blender 119. The actualattachment point of flexible hose 117 to the spout of conveyor 105, aswell as the proximity of the intake end of hose 117 to the blender bin,may vary in actual practice of system 100.

As discussed above, silica dust generated in the compartments of thetanks of trailers 101 a-101 d is collected by a set of fittings 110 andhoses 111. FIGS. 6A-6C depict this subsystem in further detail, usingtrailer 101 a as an example.

Each trailer 101 includes a set of inspection hatches 601 through thetrailer roof. In the illustrated embodiment, trailers 101 include tworows of hatches 601 that run along opposing sides of the trailer roof.(In other embodiments of trailers 101, the number and location ofinspection hatches 601 may differ. For example, some commerciallyavailable sand storage trailers utilize a single row of inspectionhatches that run along the centerline of the trailer roof.)

In addition, FIG. 6A shows optional skirts 610, which run along eachside of the depicted trailer 101. Skirts 610, which are preferablyconstructed from a durable flexible material, such as heavy plastic orcanvas, contain silica dust generated by the movement of sand throughthe lateral conveyor that runs underneath the trailer tank.

In the preferred embodiment of system 100, silica dust collection isperformed using the hatches 601 running along one side of the trailertank, although in alternative embodiments silica dust collection couldbe performed using the hatches running down both sides of the trailertank. For a given compartment, the regular hatch 602 is pulled back andreplaced with corresponding cover 603 attached an associated fitting 110(FIGS. 6B-6D).

FIG. 6B shows in further detail an example of a T-shaped (three-way)fitting 110 e interfacing with corresponding hoses 111 d and 111 e. FIG.6C shows an example of a elbow (two-way) fitting 110 a and the finalsection of hose 111 a in the trailer silica dust subsystem. Theremaining connections between the given trailer 101 and fittings 110 and111 are similar. The four-way fitting 112 used to connect trailer 101 dand silica dust control unit 106 through hose 109 is shown in detail inFIG. 6D. In each case, fittings 110 include well-known transitions andclamps to connect to hoses 111. Similar to the taps shown in FIGS.4C-4E, each fitting, such as T-shaped (three-way) fitting 110 e, elbowfitting 110 a, and four-way fitting 112, includes a slide gate forcontrolling airflow between the space within the given trailer 101 andmanifold 107.

FIGS. 7A-7C illustrate an enhancement to system 100, which includes aflexible cover system 700 for containing the silica dust generatedduring the movement of sand through the system. Preferably, flexiblecover system 700 extends over the discharge ends of trailer dischargeconveyors 102 a-102 d, the length of lateral conveyor section 103, andthe length of upwardly angled discharge conveyor section 105. (Inalternative embodiments, flexible cover system 700 may only coverportions of system 100, as necessary to effectively control silicadust.)

In the preferred embodiment, flexible cover system 700 is constructed asseparate sections 701 a-701 c and 702, as shown in FIGS. 7B and 7C.Sections 701 a-701 c cover corresponding portions of lateral conveyorsection 103 and section 702 covers upwardly angled discharge conveyorsection 105. Boots 703 are provided to allow insertion of correspondingflexible capture hoses 115 and 116 into the underlying silica dustcontainment spaces when cover system 700 is deployed. Boots 704 extendover the ends of trailer discharge conveyors 102 a-102 d.

Section 702 also includes a lateral extension 705 for covering the spoutof upwardly angled discharge conveyor section 105. A boot 707 providesfor the insertion of flexible hose 117 into extension 702 for fasteningon or near the outlet of the discharge spout of conveyor 105.

Flexible cover system 700 is preferably constructed of canvas, heavyplastic, or other flexible material that is durable, relatively easy todeploy and remove, and transportable. Preferably, the surfaces of theselected material are impervious to frac sand, as well as able towithstand the normal wear and tear expected at a fracing worksite. Whendeployed, sections 701 and 702 are attached to each other with areas ofVelcro 706 or similar attachment system, which minimizes the escape ofsilica dust at the seams between the sections.

FIGS. 8A and 8B are respectively perspective and end view diagrams of araised manifold system 800 suitable for use in frac sand dust controlsystems, such as that described above in conjunction with FIG. 1.Depending on the configuration of the dust control system, raisedmanifold 800 may be used to replace either or both of manifolds 107 and108 of FIG. 1 or be used in addition to manifolds 107 and 108.

As discussed further below, when in use in a dust collection system suchas system 100 of FIG. 1, raised manifold 800 is located generally abovelateral conveyor section 103, angled lifting conveyor section 105, thebin and/or the tub of blender 119, or a combination thereof. In theembodiment of FIG. 8A, raised manifold 800 is suspended from a supportstructure 801, which may also be used to support a cover or enclosurefor enclosing lateral conveyor section 103, lifting conveyor section105, and/or the bin and tub of blender 119.

As shown in FIGS. 8A and 8B, fluid communication with the interiorpassage of raised manifold 800 is through a set of rigid cylindricalfittings 802 coupled to taps or apertures through the manifold wall. Inother words, fittings 802 provide a plurality of ports into raisedmanifold 800 for capturing dust when negative air pressure (i.e.,suction) is applied to manifold 800, for example, by air unit 106 inembodiments of system 100. In some instances, fittings 802 are notrequired. For example, within a dust control enclosure, such as thosediscussed further below, a port into the interior of manifold 800 can bea simple aperture through the manifold wall, which can be capped whennot in use.

Two representative fittings are shown at 802 a and 802 b in FIG. 8B forreference. The actual number of fittings 802 may vary betweenembodiments, depending on such factors as the length of raised manifold800, the number of fittings 802 needed to support a range of differentdust control system configurations and dust control operations, and thediameters of the flexible conduits discussed below, among other things.In the illustrated embodiment, each fitting 802 includes a sliding gate803, two of which (802 a and 803 b) are shown in FIG. 8B for reference.The amount of air flowing through a given fitting 802 is set by thecorresponding sliding gate 803, which includes completely shutting-offair flow through an unused or unnecessary fitting 802 (with or without arigid extension or attached flexible conduit.)

Preferably, raised manifold 800 and fittings 802 are constructed fromaluminum for lightness and durability, with fittings 802 coupled toraised manifold 800 by welding or brazing. However, in alternativeembodiments, raised manifold 800, fittings 802, or both, may befabricated from other materials, such as steel or plastic, and fastenedtogether using other fastening techniques. For example, threads may beprovided on fittings 802 for mating with corresponding threads in thetaps through the manifold wall.

Moreover, while raised manifold 800 is shown as a rigid conduit having acylindrical shape, the principles of the present invention may beembodied in raised manifolds of other shapes or having different degreesof rigidity. For example, raised manifold 800 could be a flexibleconduit or have a rectangular cross-section. Generally, raised manifold800 can be any conduit or chamber having a size, shape, and rigiditysuitable to provide sufficient air flow through a sufficient number ofbranches (i.e., fittings or ports 802) as required to achieve thedesired amount of dust capture in a given dust control system having agiven configuration and a given air system rated cubic feet per minute(cfm). (In the illustrated embodiment, rigid, cylindrical raisedmanifold 800 is nominally 20 inches in diameter and fittings 802 arenominally 10 inches in diameter, based on 40000 cfm of air flow, whichcould be provided by a single air system 106 or two air systems 106providing 20000 cubic feet cfm of air flow each.)

In the illustrated embodiment of FIGS. 8A and 8B, raised manifold 800 issuspended from frame 801 by a series of periodically spaced straps 804,two of which are shown for reference at 804 a and 804 b. In alternativeembodiment, other techniques may be used to suspend raised manifold 800,such as cables, cradles, direct bolting to support frame 801, tubing orbars, among others. The particular suspension system configuration mayvary depending on such factors as the weight of raised manifold 800 andfittings 802, the number and size of fittings 802, the length anddiameter of raised manifold 800, and the ability to quickly couple anduncouple raised manifold 800 and support frame 801.

Support frame 801 can be based on any one of a number of differentconfigurations and constructions. In the embodiment illustrated in FIGS.8A and 8B, support frame 801 includes a central upper longitudinalreinforcing member 805, lower lateral longitudinal reinforcing members806 a-806 b, upper lateral longitudinal reinforcing members 807 a-807 b,and U-shaped support members 808, two of which are shown at 808 a and808 b for reference. Generally, each U-shaped support member 808includes a pair of opposing substantially straight vertical supportmembers (legs) and a curved upper section. While support frame 801 isshown as having a generally inverted U-shape horizontal cross-section,other shapes are possible, such as rectangular, triangular, or ovoid,for example. When used in a dust control system such as system 100 ofFIG. 1, the width between the vertical support member of U-shapedsupport members 808 is adapted to straddle the sides of lateral conveyorsection 103, the sides of lifting conveyor section 105, the bin and/ortub of blender 119, the chutes from a vertical sand mover, or acombination thereof.

Longitudinal reinforcing members 805, 806, and 807 and U-shaped supportmembers 808 are preferably fabricated and fastened together to maximizedurability and stability while still allowing support frame 801 to beassembled and disassembled quickly at the job site. For example,longitudinal reinforcing members 805, 806, and 807 and U-shaped supportmembers 808 may be fabricated as aluminum or steel tubing and fastenedtogether using pins or bolts. Alternatively, longitudinal reinforcingmembers 805, 806, and 807 and U-shaped support members 808 could besolid aluminum or steel bars or U-shaped beams. Support frame 801 couldalso be constructed as sections in which some components are permanentlyfastened together, for example by welding or brazing.

While raised manifold 800 is shown in FIGS. 8A and 8B as beingpositioned along the longitudinal centerline of the upper portion ofsupport frame 801, generally referencing central upper longitudinalreinforcing member 805, the lateral and vertical position of raisedmanifold 800 may vary in alternative embodiments. More specifically,raised manifold 800 may be laterally and/or vertically displaced withrespect to central upper longitudinal reinforcing member 805. The actuallocation of raised manifold 800 may be varied as needed, for example, toaccommodate different underlying structures, such as the discharge endsof trailer conveyors 102 and angled lifting conveyor 105, or variationsin the length of the flexible conduits discussed below.

In the illustrated embodiment, U-shaped frame members 808 are directlysupported by the ground through bases 809, two of which are shown at 809a and 809 b for reference. In alternative embodiments, U-shaped framemembers 808 may be supported or attached, either in whole or in part, byanother structure within the dust control system, such as lateralconveyor section 103, blender 119, or angled lifting conveyor section105. For example, U-shaped frame members 808 may be attached orsupported by the top or fastened to a lateral surface of lateralconveyor section 103.

A given fitting 802 may be used unmodified (i.e., not connected to aflexible conduit or rigid extension), connected to a flexible conduitthat extends towards the upper surface of lateral conveyor section 103,to a point along angled lifting conveyor section 105, or the bin and tubof blender 119, or may be extended lengthwise to form a longer rigidconduit for drawing in air and dust from a selected dust collectionpoint, such as a point along lateral conveyor section 103 or within thebin of blender 119. Not all fittings 802 need be used, with those notbeing used closed by the associated sliding gate 803 or capped.

FIG. 8C is a more detailed view of a portion of raised manifold 800 andsupport frame 801. Representative fittings 802, including fittings 802 aand 802 b of FIGS. 8A and 8B, are shown connected to flexible conduits.Generally, local flexible conduits 810 are used to collect air and dustat selected points along lateral conveyor section 103, along angledlifting conveyor 105, or within the bin and/or tub of blender 119.Remote flexible conduits 811 are used to collect air and dust fromwithin sand storage containers, such as trailers 101 of FIG. 1.

FIG. 8C also shows an elbow conduit 812 for coupling raised manifold 800to a source of negative air pressure, such as air system 106 of FIG. 1.Elbow conduit 812 is constructed, either in whole or in part, by a rigidor semi-rigid material such as aluminum, or a flexible material, such asrubber or polyurethane. An additional fitting 802 c and associatedsliding gate 803 c tap into elbow conduit 812.

In FIG. 8D, raised manifold 800 is shown in combination with anenclosure 814, which is configured to enclose lateral conveyor section103, angled lifting conveyor section 105, the bin and tub of blender119, or any combination of the three. Elbow conduit 812 couples with airunit 106 through a manifold system 813, which includes sections of rigidand flexible conduit, although other configurations may be used inalternative embodiments. For example, air system 106 could be connectedeither to elbow conduit 812 or directly to raised manifold 800 by aflexible conduit (i.e., eliminating elbow conduit 812, conduit system813, or both). FIG. 8D also includes optional fitting/air flow controlassemblies 818 a-818 b, which allow for additional local or remoteflexible conduits to be connected directly to conduit system 813.

The inlets of local flexible conduits 810 remain within enclosure 814,while remote flexible conduits 811 run under bottom edge 815 ofenclosure 814 or through an aperture through the sidewall of enclosure814 near bottom edge 815. In alternative embodiments, remote flexibleconduits 811 could exit enclosure 814 at different points, includingpoints higher up on the sidewalls of enclosure 814 or through theenclosure 814 roof.

Enclosure 814 is not required for using raised manifold 800, althoughuse of enclosure 814 increases the efficiency of dust capture throughmanifold 800 and flexible conduits 810, as well as generally minimizesthe escape of dust into the surrounding environment. Moreover, whenenclosure 814 is used, one or more unmodified fittings 802 can be usedfor capturing dust within the confined space. Furthermore, whileenclosure 814 is shown as having substantially clear sidewalls and anopaque roof, these are not requirements for practicing the inventiveprinciples. For example, the sidewalls may be opaque and the roof may besubstantially clear, both the roof and the sidewalls may be opaque, orboth the roof and the sidewalls may be substantially clear.

In FIG. 8E, raised manifold 800 and enclosure 814 of FIG. 8D are shownin use with an embodiment of frac sand transportation, storage, andunloading system 100 of FIG. 1 including four (4) transportation andstorage containers 101 a-101 d coupled to four (4) corresponding remoteflexible conduits 811 a-811 d extending from the bottom edge 815 of theopposing side of enclosure 814. Remote conduits 811 e-811 i extendingfrom the bottom edge 815 of the facing side of enclosure 814 may be usedfor collecting dust at other points within system 100, such as alonglifting conveyor section 105 or from within additional sand storage andtransportation containers (see FIG. 8H).

In the example of FIG. 8E, at least four (4) local conduits 810 a-810 dextend downward within enclosure 814 from raised manifold 800 to collectdust generated from the discharge of sand from four (4) containerconveyors (stingers) 102 a-102 d to lateral conveyor section 103.Preferably, in configurations where manifold 800 is generally locatedabove lateral conveyor section 103, such as those shown in FIGS. 8E and8G, manifold 800 is also located above the discharge end of trailerdischarge conveyors 102, as well.

FIG. 8F illustrates an alternative system configuration in which raisedmanifold 800 is supported above support frame 801 and outside ofenclosure 814. In this configuration, local conduits 810 run generallydown the sidewalls of enclosure 814, extend underneath enclosure edge815 or through apertures near enclosure edge 815, and then extendfurther within enclosure 814 to the corresponding dust collectionpoints. Alternatively, local conduits 810 could enter the interior ofenclosure 814 at different points, such as through one or both of theenclosure sidewalls or through the enclosure roof.

In the supported configuration of FIG. 8F, raised manifold 800 issupported by periodically spaced u-shaped cradles 819, two of which areshown at 819 a and 819 b for reference. Cradles 819 are fastened tocentral upper longitudinal reinforcing member 805 of support frame 801,for example, by bolts or pins. Alternatively, raised manifold 800 couldbe directly fastened to upper longitudinal reinforcing member 805 orfastened to support structure 801 using another technique. Furthermore,while raised manifold 800 is shown positioned along the centerlinegenerally defined by central upper longitudinal reinforcing member 805,it could be laterally and/or vertically displaced from the centerline inalternative embodiments.

In FIG. 8G, the supported configuration of raised manifold 800 andenclosure 814 are shown in use with an embodiment frac sandtransportation, storage, and unloading system 100 of FIG. 1 includingfour (4) transportation and storage containers 101 a-101 d coupled tofour (4) corresponding remote flexible conduits 811 a-811 d coupled tocorresponding fittings 802 on the opposing side of raised manifold 800.Remote conduits 811 e-811 j extending from fittings 802 on the facingside of enclosure 814 may be used for collecting dust at other pointswithin system 100, such as along lifting conveyor section 105 or fromwithin additional sand storage and transportation containers.

In the example of FIG. 8G, at least four (4) local conduits 810 a-810 dextend downward outside of the sidewall of enclosure 814, extendunderneath enclosure edge 815 or through apertures near enclosure edge815, and then extend upward within cover 814 to collect dust generatedfrom the discharge of sand from four (4) container conveyors (stingers)102 a-102 d to lateral conveyor section 103.

An alternative configuration is shown in FIG. 8H, where manifold 800remains outside of enclosure 814 and is supported by support structure801, but is now located lower down the side of the support structure801. While manifold 800 is shown generally at the point where U-shapedsupport members 808 transition from a curve to vertical support members,manifold 800 can be placed at any point between the very top of supportstructure 801 (FIGS. 8F and 8G) and the ground. In addition, manifold800 can be positioned on either side of support structure 801, as needfor a particular worksite or dust control system configuration.

In the embodiment of FIG. 8H, manifold 800 is preferably secureddirectly to support frame 801 by bolts, pins, or a similar fasteningtechnique. Remote flexible conduits 811 then extend over the uppercurved portion of support structure 801 and enclosure 814. In someembodiments, flexible conduits 810 could extend through the top portion(roof) of enclosure 814 to capture dust within the enclosure interior.Local flexible conduit 810 e is an example of a flexible conduitextending through the top portion of enclosure 814.

FIG. 8I illustrates an example in which remote conduits 811 extend fromboth sides of raised manifold 800. In this example, raised manifold 800is shown in the configuration of FIGS. 8A-8E, although the sameprinciples apply to the configuration shown in FIGS. 8F-8G. Here, three(3) remote conduits 811 a-811 c service three (3) sand transportationand storage containers 101 a-101 c and two (2) remote conduits 811 d-811e service two (2) portable silos or vertical sand movers 816 a-816 b.(The number of sand sources, such as transportation and storagecontainers 101 and portable silos/vertical sand movers 816 may vary inactual practice.) Within enclosure 814, at least one local flexibleconduit 810 or extended fitting 802 collects dust generated around eachof the sand discharge points from trailer conveyors 102 a-102 b and thesand discharge points from portable silo chutes 817 a-817 b.

The principles of the present invention are also embodied in a raisedmanifold and enclosure system more specifically adapted for containingand collecting dust generated in and around the bin and tub of blender119. One such system is shown in FIG. 9A, which includes a raisedmanifold 900 suspended below a support structure 901 by a set of strapsor cables, two of which are shown at 910 a and 910 b for reference.Preferably, the construction of support structure 901 and straps/cables910 are similar to those of support structure 801 and straps/cables 804discussed above, although that is not a strict requirement of practicingthe inventive principles. Support structure 901 also supports anenclosure 907, which is preferably similar in construction to enclosure814 discussed above.

In the embodiment shown in FIG. 9A, raised manifold 900 includes a setof fittings, such as fittings 902 a and 902 b, which are in fluidcommunication with the interior passage through raised manifold 900.Similar to fittings 802 discussed above, fittings 902 provide aplurality of ports into raised manifold 900 for capturing dust whennegative air pressure (i.e., suction) is applied to manifold 900, forexample, by air unit 106 in embodiments of system 100. Each fitting 902is associated with an air flow control device, which could be a gate,butterfly valve, ball valve, or similar device, controls air flowcontrol through the corresponding fitting 902. (Air flow controlpreferably extends from a complete airflow shut-off to a maximumallowable flow through the given fitting 902 under the given systemoperating conditions.) In the illustrated embodiment, sliding gates 903a and 903 b are shown as an example. While four (4) fittings 902 areshown in the exemplary embodiment of FIG. 9A, the number of fittings 902may vary in actual applications, depending on the dust-capturerequirements.

Fittings 902 can be used unmodified (e.g., without a flexible conduit orrigid extension), with a rigid extension, or in conjunction with aflexible conduit or rigid extension. Unmodified or extended fittings 902are particularly suitable for capturing dust contained within enclosure907. Fittings 902 connected to flexible conduits are suitable forcapturing dust at one or more points within enclosure 907, as well asone or more points outside of enclosure 907. Not all fittings 902 needbe used and unused fittings 902 can be shut-off using the correspondingsliding gates 903.

The construction of raised manifold 900 is preferably similar to that ofraised manifold 800 discussed above. As with raised manifold 800,characteristics such as shape, fabrication material, degree of rigidity,and so on, may vary from embodiment to embodiment of the presentinventive principles.

As shown in FIG. 9A, all four (4) exemplary fittings 902 are coupled toa corresponding set of four (4) flexible conduits. Two (2) fittings 902are connected to local flexible conduits 904 a and 904 b, which extenddownward within cover 907 for capturing dust in the areas around the binand tub of blender 119 (see FIG. 9E). In addition, two other fittings902 are coupled to remove flexible conduits 905 a-905 b, which extendunder the bottom edge 909 or through an aperture close to bottom edge909 of enclosure 900. Remote flexible conduits 905 may be used tocapture dust at other points around a frac sand storage and movementsystem, for example, dust within a trailer 101, dust generated alonglateral conveyor system 103, or dust generated along angled liftingconveyor 105 of an embodiment of system 100 of FIG. 1. In alternativeembodiments, remote flexible conduits 905 could exit enclosure 907 atdifferent points, including points higher up on the sidewalls ofenclosure 907 or through the enclosure 907 roof.

A elbow-shaped conduit 906 couples raised manifold 900 to an air system106, which is similar to those discussed above. In one particularconfiguration shown in FIGS. 9B and 9C, rigid elbow-shaped conduit 906communicates with an air system 106 through a manifold system 908 formedof both rigid and flexible sections of conduits, although otherconfigurations may be used in alternative embodiments. For example, airsystem 106 could be connected either to elbow-shaped conduit 906 ordirectly to raised manifold 900 through a flexible conduit or conduit.

FIG. 9D shows an alternative configuration where raised manifold 900 issupported above the roof of enclosure 907 by frame 901 and u-shapedcradles 920 a-920 b. In this configuration, local conduits 904 rungenerally down the sidewalls of enclosure 907, extend underneathenclosure edge 909 or through apertures near enclosure edge 909, andthen extend further within enclosure 907 to the corresponding dustcollection points. Alternatively, local conduits 904 could enter theinterior of enclosure 907 through one or both of the enclosure sidewallsor through the roof. In addition, while cradles 920 are shown asu-shaped in the illustrated embodiment, different cradle shapes may beused in alternate embodiments.

A further alternative configuration is shown in FIG. 9E, where manifold900 remains outside of enclosure 907 and is supported by supportstructure 901, but is now located lower down the side of the supportstructure 901. While manifold 900 is shown generally at the point wheresupport structure 901 transitions from a curve to vertical supportmembers, manifold 900 can be placed at any point between the very top ofsupport structure 901 (FIG. 9D) and the ground. In addition, manifold900 can be positioned on either side of support structure 901, as needfor a particular worksite or dust control system configuration. FIG. 9Dalso shows optional fittings/air flow control assemblies 913 a-913 b,which allow additional local or remote flexible conduits to be connecteddirectly with manifold system 908.

In the embodiment of FIG. 9D, manifold 900 is shown supported by a setof cradles 920 a-920 b extending outwardly from support frame 901,although manifold 900 could also be secured directly to support frame901 by bolts, pins, or a similar fastening technique. Remote flexibleconduits, such as remote flexible conduit 905 b, can then extend overthe upper curved portion of support structure 901 and enclosure 907. Insome embodiments, one or more local flexible conduits 904, such as localflexible conduit 904 b, could extend through the top portion ofenclosure 907 to capture dust within the enclosure interior.

FIG. 9F illustrates an alternative frac sand transportation, storage,and unloading system 911 including a frac sand silica dust controlsystem suitable for use with either of the configurations of raisedmanifold 900 shown in FIGS. 9A and 9D. Preferably, enclosure 907encloses the bin, the tub, or both the bin and tub of blender 119. InFIG. 9F, enclosure 907 encloses both the blender bin and the blendertub, as generally shown in broken lines. At least one fitting 902, whichmay be unmodified, extended, or connected to a local flexible conduit904, as shown in FIG. 9F, collects dust contained by enclosure 907.

In the system of FIG. 9F, the container conveyors (stingers) 102 a-102 cassociated with trailers 101 a-101 b extend through apertures in thesidewalls of enclosure 907 and discharge sand directly into the bin ofblender 119. Preferably, manifold 900 is located above the discharge endof container conveyors 102 a-102 c (or in embodiment using one or moresilo chutes, above the discharge ends of the silo chutes). In addition,FIG. 9E provides an example where two (2) manifolds and two (2) airsystems are used to collect dust at various points around the system.

Specifically, air system 106 a and manifold 912 are used to collect dustwithin the compartments of trailers 101 a-101 b. Air system 106 b andraised manifold 900 capture dust within enclosure 907, as well asprovide a remote flexible conduit 905 for collecting dust within some ofthe compartments of trailer 101 a. Raised manifold 900 and manifold 912may also be coupled together to create a unified conduit system servicedby either or both of air systems 106 a-106 b.

FIG. 9F only shows one possible use of raised manifold 900. Raisedmanifold 900 can be used alone to collect dust around the bin and tub ofa fracing blender, provide negative air pressure to one or more localflexible conduits 905 for collecting dust along a lateral conveyor,lifting conveyor, a container conveyor, or silo chute, and/or providenegative air pressure through one or more remote flexible conduits 905for collecting dust within a sand trailer or portable sand silo. Raisedmanifold 900 may also be use in conjunction with raised manifold 800 andenclosure 814. Advantageously, when raised manifolds 800 are 900 areused in combination, a wide range of options are available forcollecting dust around a given frac sand transportation, storage, andhandling system.

In sum, the principles of the present invention provide for theefficient capture and removal of silica dust generated during theoffloading of frac sand at a worksite. Silica dust removal is performednear, but not limited to, substantial sources of hazardous silica dust,including at trailer to trailer conveyor sand transfer point, each pointof transfer from the trailer discharge conveyors and the lateral siteconveyor, and points along the lifting/discharge conveyor. Theembodiments of the inventive principles are scalable, and can be appliedto any discharging system serving single or multiple frac sand storagetrailers and can be implemented with various commercially availablecyclone/baghouse silica dust removal systems. Moreover, theconfiguration and construction of these embodiments are also variable,allowing silica dust control to be effectively implemented under widelyvarying worksite conditions.

Although the invention has been described with reference to specificembodiments, these descriptions are not meant to be construed in alimiting sense. Various modifications of the disclosed embodiments, aswell as alternative embodiments of the invention, will become apparentto persons skilled in the art upon reference to the description of theinvention. It should be appreciated by those skilled in the art that theconception and the specific embodiment disclosed might be readilyutilized as a basis for modifying or designing other structures forcarrying out the same purposes of the present invention. It should alsobe realized by those skilled in the art that such equivalentconstructions do not depart from the spirit and scope of the inventionas set forth in the appended claims.

It is therefore contemplated that the claims will cover any suchmodifications or embodiments that fall within the true scope of theinvention.

What is claimed is:
 1. A system for controlling dust during hydraulicfracturing operations comprising: a conveyor adapted to transport sandfrom a sand source to a blender, the conveyor including a conveyorframe; an air system for providing suction; a manifold coupled to theair system; at least one conduit having a first end coupled to the airsystem through the manifold and a second end for capturing dust whensuction is applied to the first end by the air system through themanifold; and a self-supporting cover system having a first portion anda second portion, the first portion of the cover system being adapted toenclose a lateral section of the conveyor disposed adjacent to the sandsource, the first portion of the cover system comprising a set of firstsidewalls supported by a first set of cover frames straddling the sidesof the lateral conveyor section and having bases on the ground, whereineach cover frame of the first set of cover frames includes an uppersection connected between a pair of spaced-apart vertical portions, thepair of vertical portions being adapted to straddle the lateral conveyorsection, and wherein a lower end of each respective vertical portion isconnected to, and supported by, a respective individual base configuredto rest on the ground, wherein each respective individual base isdirectly connected to the lower end of the respective vertical portionand is not directly connected to any other individual base, any othervertical portion, or any other cover frame of the first set of coverframes, wherein each respective vertical portion is directly connectedto the respective individual base and the respective upper section, andis not directly connected to any other individual base, any othervertical portion or any other cover frame of the first set of coverframes, and wherein the individual bases, vertical portions and uppersection are unconnected to the lateral conveyor section; the secondportion of the cover system being adapted to enclose at least a portionof at least one of a blender bin and a blender tub, the second portionof the self-supporting cover system comprising a set of second sidewallssupported by a second cover frame based on the ground, wherein: adischarge end portion of the conveyor extends through one of the secondsidewalls such that a discharge end of the conveyor is disposed above atleast a portion of the at least one of the blender bin and the blendertub; and wherein the manifold has a first portion and a second portion,the first manifold portion being supported by the first set of coverframes such that the first portion of the manifold is positioned above,and parallel to, the lateral conveyor section, and the second manifoldportion being supported by the second cover frame above at least aportion of the at least one of the blender bin and the blender tub, andwherein the second manifold portion is displaced relative to acenterline of the second cover frame so as to accommodate the at leastone of the blender bin and the blender tub; and the at least one conduitextends from the manifold such that the second end of the at least oneconduit is disposed within the cover system above the discharge end ofthe conveyor and above the at least one of the blender bin and theblender tub.
 2. The system of claim 1, wherein at least one of the setof first sidewalls or the set of second sidewalls is formed of flexiblematerial.
 3. The system of claim 1, wherein the discharge end of theconveyor comprises a spout.
 4. A dust control system comprising: aconveyor for transporting sand and including a conveyor frame and adischarge end; an air system for generating a negative air pressure; amanifold coupled to the air system and having a plurality oflongitudinally spaced apart ports; a self-supporting cover systemincluding a cover frame and a plurality of flexible sidewalls supportedon the frame and adapted to cover the discharge end of the conveyor andat least a portion of at least one of a blender bin and a blender tub;the cover frame comprising a set of cover frame members, wherein eachcover frame member includes an upper section connected between a pair ofspaced-apart vertical portions, with a lower end of each respectivevertical portion being connected to, and supported by, a respectiveindividual base configured to rest on the ground, wherein eachrespective individual base is directly connected to the lower end of therespective vertical portion and is not directly connected to any otherindividual base, any other vertical portion, or any other cover framemember of the cover frame, wherein each respective vertical portion isdirectly connected only to the respective individual base and therespective upper section, and is not directly connected to any otherindividual base, any other vertical portion or any other cover framemember of the cover frame, and wherein the individual bases, verticalportions and upper section are unconnected to the conveyor, conveyorframe, and the at least one of the blender bin and the blender tub;wherein the cover frame straddles the conveyor such that the cover frameof the self-supporting cover system is unconnected to the conveyor orthe conveyor frame and a portion of the conveyor extends through one ofthe flexible sidewalls such that the discharge end of the conveyor isdisposed above at least a portion of the at least one of the blender binand the blender tub, the manifold supported above the ground by thecover frame of the self-supporting cover system to be positioned above,and parallel to, the conveyor, and displaced relative to a centerline ofthe cover frame of the cover system so as to accommodate the at leastone of the blender bin and the blender tub; and a plurality of hosescoupled to the air system by way of corresponding ports of the manifoldand extending through a flexible sidewall of the self-supporting coversystem into an interior of the self-supporting cover system forcapturing dust within the interior of the self-supporting cover systemwhen the negative air pressure is applied to the hoses by the airsystem, wherein an inlet of at least one of the hoses is disposedadjacent the discharge end of the conveyor and above a portion of the atleast one of the blender bin and the blender tub.
 5. The system of claim4, wherein the hoses are flexible.
 6. A system for processing sandduring hydraulic fracturing comprising: a source of sand; a blenderincluding a blending bin; a conveyor for transporting sand from thesource to the blender and having a conveyor frame and a discharge pointover the blender bin; a self-supporting enclosure including an enclosureframe that straddles the conveyor and the conveyor frame and a pluralityof sidewalls supported on the enclosure frame and enclosing the blenderbin and the discharge point of the conveyor, wherein the enclosure frameof the self-supporting enclosure comprises a set of enclosure framemembers, wherein each enclosure frame member includes an upper sectionconnected between a pair of spaced-apart vertical portions, with a lowerend of each respective vertical portion being connected to, andsupported by, a respective individual base configured to rest on theground, wherein each respective individual base is directly connected tothe lower end of the respective vertical portion and is not directlyconnected to any other individual base, any other vertical portion, orany other enclosure frame member of the enclosure frame, wherein eachrespective vertical portion is directly connected to the respectiveindividual base and the respective upper section, and is not directlyconnected to any other individual base, any other vertical portion orany other enclosure frame member of the enclosure frame, and wherein theindividual bases, vertical portions and upper sections are unconnectedto the conveyor or the conveyor frame and wherein a portion of theconveyor extends through one of the sidewalls such that the dischargeend of the conveyor is disposed above at least a portion of the blenderbin; an air system for generating negative air pressure; a manifoldcoupled to the air system and at least partially supported above theground and above the conveyor and parallel to the conveyor by theenclosure frame of the self-supporting enclosure, wherein the manifoldincludes a plurality of longitudinally spaced apart ports, and whereinthe manifold is displaced relative to a centerline of the enclosureframe to accommodate the blender bin; and a plurality of hoses, eachhose being coupled to the air system through a corresponding one of theports of the manifold for capturing dust within the self-supportingenclosure when negative air pressure is applied by the air system,wherein at least one of the plurality of hoses extends through asidewall of the self-supporting enclosure such that an inlet of the atleast one hose is disposed above the discharge end of the conveyor andabove a portion of the blender bin.
 7. The system of claim 6, whereinthe conveyor comprises a spout having an outlet forming the dischargepoint over the blender bin.
 8. The system of claim 6, wherein theplurality of sidewalls of the self-supporting enclosure are formed fromat least one piece of flexible material.
 9. The system of claim 6,wherein the conveyor comprises an upwardly-angled conveyor section of aconveyor system comprising the upwardly-angled conveyor section and alateral conveyor section.
 10. The system of claim 6, wherein theconveyor directly transports sand from the source to the blender.